Engine Performance problem
1999 Ford Festiva 4 cyl Two Wheel Drive Manual 70000 miles

hi, my ford festiva is pinging/pinking whenever the accelerator is depressed more than half. it is also going through a lot of oil. it seemed to get better when we added more oil, however it has never resolved and is getting worse. any advice of where to start? i've checked the spark plug leads and spark plugs and they are all ok